This invention relates generally to the field of magnetic data storage devices, and more particularly, but not by way of limitation, to improving data transfer rate performance by partitioning disc drive read/write electronic circuitry.
Disc drives are used as primary data storage devices in modern computer systems and networks. A typical disc drive comprises one or more rigid magnetic storage discs which are journaled about a spindle motor for rotation at a constant high speed. An array of read/write transducing heads are provided to transfer data between tracks of the discs and a host computer in which the disc drive is mounted. The heads are mounted to a rotary actuator assembly and are controllably positioned adjacent the tracks by a closed loop servo system.
Continued demands for ever greater levels of data transfer performance at lower cost have led disc drive manufacturers to seek ways to enhance the functionality of the electronics used to control the reading and writing of data. Such enhancements have included, at the integrated circuit (IC) level, the use of successively smaller lithography (i.e., the individual size and spacing of the individual circuit elements, such as transistors) and using reduced source voltage levels.
While such efforts have been found to enhance the digital signal processing capabilities of the disc drive electronics, designers have been challenged to provide the corresponding requisite analog signal processing capabilities without significantly increasing system cost. What is needed is an improved approach to providing disc drive read/write electronics that allows designers to incorporate state of the art advancements in digital signal processing without being encumbered by limitations in effecting the requisite analog processing functionality.
The present invention provides an apparatus for improving disc drive data transfer performance. In accordance with preferred embodiments, a disc drive comprises a rotatable disc to which data are stored using a head that is controllably positioned using an actuator assembly.
Mounted to the actuator assembly is an analog pre-processor integrated circuit device that incorporates circuitry to carry out analog processing functions to read and write data. The pre-processor carries out write current driving, readback signal amplification, prewrite compensation, frequency-domain filtering, and equalization.
A digital post-processor integrated circuit device, preferably supported on a printed circuit board mounted to an exterior surface of the disc drive, incorporates circuitry to carry out digital signal processing functions. The post-processor carries out Viterbi detection, decoding, error detection and correction, buffering, host interface functions, and data encoding and serialization. Additional circuitry, such as a conventional programmable system processor and conventional motor driver circuitry, can be used to perform remaining servo positioning control functions.
In this way, lower cost, older technology fabrication techniques which accommodate larger lithography and higher operating voltages can be readily used to provide the analog features and performance necessary to match the higher performance, state-of-the art digital features incorporated into the post-processor. Tradeoffs between the analog and digital features of prior art designs, which typically use an analog preamplifier/driver, a mixed analog and digital read/write channel, and a digital interface, are eliminated. Instead, the traditional preamplifier/driver is further configured to carry out prewrite compensation, AGC, filtering and equalization tasks from the read/write channel. The post-processor forms a new digital channel/interface to handle all digital read/write processing as well as buffering and host interface tasks. Thus, the conventional three chip read/write system becomes an optimized, two chip processor, enhancing transfer performance at lower cost.